The present invention relates generally to magnetic circuit components and more particularly to magnetic components for mounting on a circuit board housed within an enclosure. The present invention also relates to enclosed electronic devices.
Magnetic components including a magnetically permeable core and one or more conductive windings positioned near the core are known in the art. Such components are used in conventional inductors and transformers in a variety of electronic applications. Magnetic components of this type can generally be configured for surface mounting on a circuit board for use in an electrical circuit. Common applications for such devices include power supplies and power regulators for electrical lighting applications. Typically, in these applications, the circuit board and electronic components disposed thereon are housed within an enclosure.
Some conventional magnetic components configured for mounting on a circuit board generally include a core structure having one or more core legs extending outward from a core body. Each core leg has a leg height, a leg length and a leg width. A conductive winding including one or more turns of a conductive wire can be positioned around any one or more of the core legs. In some conventional applications, primary and secondary windings are positioned around a core leg to form a transformer. In many conventional applications, the conductive winding or windings are positioned first on a bobbin structure, or coil former. The bobbin structure includes an axial opening, and a core leg can be inserted into the axial opening such that the bobbin structure and the conductive coil both surround the core leg.
FIG. 1 illustrates a conventional magnetic component including a core 102 and a bobbin structure 106. A conductive winding 104 is positioned around the bobbin structure 106. The core 102 illustrated in the conventional magnetic component 100 in FIG. 1 is a standard E-core having a middle core leg of substantially the same height as the core body and the outer core legs. The bobbin 106 also includes a bobbin end flange 107. FIG. 2 illustrates a cross-sectional view of Section 2-2 from FIG. 1, showing a conventional magnetic component 100 mounted on a circuit board 168 inside an enclosure 164 to form an electronic device.
Because magnetic circuit components in electronic devices generate heat during use, it is generally desirable to dissipate heat away from such components to ensure proper operation and to reduce the risk of component failure or fire inside the enclosure. However, close proximity between magnetic circuit components and enclosure walls in compact electronic devices can make efficient heat dissipation difficult to achieve.
Additionally, in many electronic applications, a magnetic component such as an inductor or transformer forms the tallest circuit component mounted on a circuit board in an electronic device. Thus, any enclosure formed to surround the circuit board must include an interior height sufficient to accommodate the height of the tallest circuit component, i.e. the transformer or inductor. Additionally, the growing trend of miniaturization in the electronics industry seeks to reduce the electronic device profile of enclosed circuit boards, resulting in narrow spaces between inner enclosure walls and the surfaces of magnetic components mounted on the circuit board housed within the enclosure. Thus, it is desirable to produce magnetic components with reduced profile for reducing electronic device size. However, the goal of miniaturizing electronic devices by reducing the space between components and enclosure walls can make the goal of efficient heat dissipation more difficult to achieve.
Others have tried to address the problem of dissipating heat from conventional magnetic components by providing a thermal gap-filler, or bonding material between the magnetic component and the enclosure wall. By thermally connecting the magnetic component to the enclosure wall, the enclosure wall can act as a heat sink to dissipate heat. Heat generated in the magnetic component transfers from the core through the thermal gap-filler into the enclosure wall, where the heat can be further dissipated to the surrounding environment or to heat dissipation structures such as cooling fins. Heat can then be removed from the enclosure or cooling fins by natural or forced convection and/or radiation to the ambient environment.
Referring again to the conventional configuration illustrated in FIG. 2, a gap is defined between the core 102 and the interior enclosure surface 166 of enclosure wall 164. The gap can be filled with a thermally conductive gap-filler 170. The gap-filler 170 provides a thermal bridge for heat flux to pass from the magnetic component 100 to the enclosure 164. However, because the conductive winding 104 and bobbin structure 106 extend above the core 102, as seen in FIG. 2, gap-filler 170 includes at least two thicknesses. A first gap filler thickness 174a extends between the interior enclosure surface 166 and the core 102. A second gap-filler thickness 174b extends between the interior enclosure surface 166 and the conductive winding 104. The conventional configuration requiring multiple gap-filler thicknesses can provide inadequate heat dissipation because the thermal resistance is increased between core 102 and enclosure 164 through the greater second gap-filler thickness 174b. Additionally, much of the heat generated by the magnetic component 100 is present in the core 102. Thus, the excessive distance between core 102 and enclosure 164 prevents optimal heat dissipation. Further, the height to which conductive winding 104 and bobbin structure 106 extend above core 102 prevents reduction in the electronic device profile.
What is needed, then, is an improved magnetic component for an electronic circuit for dissipating heat from the magnetic component. Also needed is an improved electronic device having improved heat dissipation and reduced electronic device profile. Additionally, methods of manufacture associated with the improved magnetic component and electronic device are also needed.